The present invention concerns a force transmission or transport device. As force transmission means, the device comprises a line of force transmitting elements, guide means for guiding the force transmitting elements along a redetermined course and at least one drive, whereby the drive acts upon force transmitting elements locally and displaces these in the area of the drive along the predetermined course and whereby the driven elements displace further elements in the line by pushing or pulling them.
The force transmitting elements may be connected to each other forming a chain, the connections between the elements having more or less clearance. Connected force transmitting elements can act on each other in a pulling manner, or if they have a suitable form and suitable guide means are provided, also in a pushing manner. On the other hand, the force transmitting elements may be unconnected. For unconnected force transmitting elements, it is necessary to provide guide means along the whole course (e.g. guiding channel or rails) and force transmission is only possible by means of pushing.
For transport purposes, the force transmission elements are at least partly equipped with transport means or can be coupled to such means. The transport means are e.g. grippers for gripping individual objects, loading platforms, or loading containers displaceable along the predetermined course.
Suitable drives for force transmission means as described above are, for example, sprockets meshing with the force transmitting elements or between the force transmitting elements (positive engagement) and driving these along a mostly circular section of the course.
If the force transmission means of a force transmission or transport device of the kind described above comprises mutually connected elements, with non-negligible clearance between the elements or if the force transmission means comprises unconnected elements, the distances between the elements are dependent on the load. On loaded sections of the course (e.g. between a drive and a power take-off) lines of pulled elements have the relatively largest distances between each other while lines of pushed elements have the relatively smallest distances between each other. On sections of the course where there is no load, the distances between the elements are not precisely defined and are possibly dependent on changing outer or external circumstances.
For preventing such undefined distances between force transmitting elements, force transmission means that are closed in themselves are tensioned. For example, tensioning of chains, chain adjusters, can be done with passively rotating sprung sprockets or chain channels that are elastically deformable in a longitudinal direction and designed to be slightly longer than the chain running inside them.
This kind of pre-tension between force transmission means (chain) and guide means (chain adjusters or longitudinally elastic channel) is possible only for a force transmission means which extends substantially without gaps over a predetermined course being closed in itself. It is not applicable for a force transmission means with two ends that are moved to and fro on a predetermined course. It is not applicable for a line of unconnected force transmitting elements that are displaced along a predetermined course in varying numbers. It is also not applicable for a local pretension of the force transmission means.